A catalyst for preparing low isotactic index polypropylene

Abstract

The invention relates to a catalyst for preparing low isotactic index polypropylene and its application, including active components, cocatalysts and external electron donor compounds. In the catalyst, the external electron donor of the organic amine compound is rationally matched with the active component to realize the preparation of the low-isotactic polypropylene, and the obtained product has high polymerization activity. During the preparation process, a molecular weight regulator can be used to adjust the length of the molecular chain to keep the product at a low tacticity, and ethylene or other α-olefins can also be added to copolymerize with propylene to further adjust the crystallinity of the product. The tacticity of polypropylene can be significantly reduced without changing the polymerization reaction conditions, and has the advantages of simplicity, effectiveness, easy implementation, and convenient brand switching.

Description

technical field [0001] The present invention relates to a catalyst for preparing polypropylene with low isotactic index and its application, more specifically, to an external electron donor with low stereospecificity and its application. Background technique [0002] In the field of polymers, high isotactic polypropylene (i-PP) generally refers to polypropylene products with an isotactic index (expressed by xylene insoluble content) ≥ 90%. There is no strict definition for low isotactic polypropylene (Li-PP), which generally refers to polypropylene series products between atactic polypropylene (a-PP) and high isotactic polypropylene (i-PP), including Polypropylene based product with low comonomer content. Compared with high isotactic polypropylene, low isotactic polypropylene has the characteristics of low density, good toughness, low temperature softness, low heat sealing temperature, and easy processing; compared with traditional atactic polypropylene, low isotactic polyp...

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Problems solved by technology

[0004] Patent document CN1205236C has reported a method for separating the by-product low-isotactic polypropylene when producing high-isotactic polypropylene. The low-isotactic polypropylene obtained by the method is only a by-product, so the yield is relatively low; patent document CN1137158C and US4710563 reports the processing method of low isotactic polypropylene, can obtain the product of uniform particle, but does not relate to the preparation method of low isotactic polypropylene; Patent CN1067693C, CN1122048C, CN1315885C, US4777216, patent application CN200410017170.7 and patent application CN02160046. 5 reported the preparation method of Ziegler-Natta catalyst for low isotactic polypropylene, which mainly realizes the preparation of catalyst for low isotactic polypropylene by adding an internal electron donor with a low isotactic index or changing the activated form of the carrier. The catalyst prepared by the method has the disadvantages of low polymerization activity and high ash content of the synthesized polymer

[0005] Patent documents EP1023339B1, US4754004, US5391789, US4542199, EP283739, US4931417, EP399347, US6028140, US6121377 and US6683150B1 report the method for preparing low-isotactic polypropylene by using different metallocene catalysts. The prepared low-isotactic polypropylene has low isotacticity, Uniform comonomer distribution, adjustable molecular weight, good transparency, etc. However, metallocene catalysts and co-catalysts (MAO) are expensive and the production cost is high

At present, there are few reports on the direct synthesis of low-isotactic polypropylene products by selecting a low-stereoregular Ziegler-Natta catalyst system and adopting an appropriate process

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